1. Field of the Invention
The present invention relates to a synchronization controller and particularly to a synchronization controller having a function of solving a shock generated in a synchronization start block during a synchronization control.
2. Description of the Related Art
In a machine in which a synchronization control is performed to drive a plurality of axes in a synchronized state, a movement amount is set to each of a master axis as a reference and a slave axis operated while being synchronized with the master axis and the slave axis is operated by using a ratio between the master axis movement amount and the slave axis movement amount as a speed ratio. In that case, if the slave axis starts to be synchronized with the master axis which is currently moving, the slave axis which has been in a stopped state so far tries to reach, with rapid acceleration, a speed obtained by multiplying the speed of the master axis by the speed ration. Thus, there is a case in which a shock is generated when the synchronization starts.
In order to prevent such a shock from being generated in the slave axis at a time when the synchronization starts, JP 2006-164009 A discloses a prior art technique to use an instruction which gradually changes a synchronization magnification between a master axis and a slave axis. Here, a shock to be generated when a driving operation starts at a speed ratio between the master axis and the slave axis is prevented in a manner such that the synchronization magnification with respect to the master axis is gradually increased from zero until the slave axis in the stop state reaches a desired synchronized speed based on instructions of a master axis position at a time when the slave axis in the stop state starts to be accelerated, a master axis movement amount and a slave axis movement amount used for the gradual acceleration to the desired synchronization speed, and a speed ratio between the master axis and the slave axis at a time when the acceleration ends.
FIG. 6 is a diagram illustrating an operation when the slave axis in the stop state is synchronized with the master axis in the technique disclosed in JP 2006-164009 A.
In this technique, regarding a synchronization magnification changing instruction, five parameters including an initial synchronization magnification αa (zero in the stop state), a final synchronization magnification αb, a master axis movement amount Dm, a slave axis movement amount Ds, and a master axis movement amount da before start of synchronization magnification change (where a remaining master axis movement amount db after the change of synchronization magnification is zero) are set. Further, regarding a synchronization operation instruction, two parameters including a master axis movement amount Dm2 and a slave axis movement amount Ds2 are set.
By the setting of the parameters in the above-described two instructions (the synchronization magnification changing instruction and the synchronization operation instruction), a synchronization control is performed in which an operation based on the synchronization magnification changing instruction first starts after the master axis moves by a distance da and the synchronization magnification gradually increases from zero to αb when the slave axis moves completely by the slave axis movement amount Ds. Subsequently, an operation based on the synchronization operation instruction starts so that the slave axis moves by a distance Ds2 at a constant synchronization magnification αb.
By such a synchronization control, the slave axis is gradually accelerated by the operation based on the synchronization magnification changing instruction and attains a synchronization speed at the start time of synchronization operation instruction when the operation based on the synchronization magnification changing instruction ends, and hence the synchronization of the slave axis can be started by a smooth acceleration operation.
However, in an instruction of changing the synchronization magnification for gradually increasing the synchronization magnification with respect to the master axis from zero, if the slave axis movement amount is erroneously set to a large value with respect to instruction values of the master axis position at which the slave axis in the stop state starts to be accelerated and the master axis movement amount required for gradual acceleration to the desired synchronization speed, an acceleration becomes larger than a desired acceleration, thereby arising a problem in that a mechanical shock is generated when the synchronization is started.
More specifically, when the slave axis movement amount Ds is erroneously set in the synchronization magnification changing instruction, for example, when the slave axis movement amount is set to be slightly large, a problem arises in that the acceleration of the operation based on the synchronization magnification changing instruction increases as shown in FIG. 7A. Further, when the slave axis movement amount is erroneously set to be larger, a problem arises in that the speed of the operation based on the synchronization magnification changing instruction is excessively accelerated or decelerated as shown in FIG. 7B.
Further, since the master axis position at which the slave axis in the stop state starts to be accelerated is set by the synchronization magnification changing instruction of gradually increasing the synchronization magnification with respect to the master axis from zero, it is not possible to set the master axis position, in other words, the original synchronization start position at a time point in which the set synchronization magnification is attained.
That is, as described above by referring to FIG. 6, in the synchronization magnification changing instruction, the master axis movement amount da before start of synchronization magnification change is set to set the movement start position of the operation based on the synchronization magnification changing instruction. In the subsequent synchronization operation instruction, the operation based on the synchronization operation instruction needs to be started immediately after the operation based on the synchronization magnification changing instruction is completed. For that reason, synchronization operation instruction for starting the synchronization does not allow the position of the master axis (a position indicated by “Sp” of FIG. 6) to be set directly.